In 1959, a team of experienced and healthy mountaineers perished in the mysterious Dyatlov Pass incident. Miles from anywhere, they'd torn their way out of their tent, fled half-naked into the night, then died in the freezing cold, scattered in the surrounding snow and woods. Alarming oddities were in abundance—evidence of crushing injuries, missing organs, radioactivity—but the authorities, first Soviet and more recently Russian, concluded that an avalanche occurred.
They're probably right, conclude researchers who explain how an avalanche was possible despite the light gradient and might have led to such a puzzling state of affairs. A close examination of the topography and climate conditions, and a modern understanding of slab avalanches, make for a mundane but no less horrible end to the expedition.
The simulated snow slab reached a velocity around 2 m/s upon impact. At this velocity, an impact on a human thorax of a typical snow block with a volume of 0.125–0.5 m3 and density 400 kg/m3 results in a maximum thorax deformation between 28% and 34%, corresponding to the lower range of values reported from crash tests by Kroell et al. for a 10 kg mass impacting the thorax at a speed of 7 m/s. According to the Abbreviated Injury Scale (AIS), these deflections would mostly lead to non-fatal thoracic injuries from moderate to severe, in agreement with the autopsy report of the Dyatlov-incident criminal investigation. Such injuries are not usually observed in avalanche victims, because impacts rarely occur against stiff obstacles. In the Dyatlov case, the victims were trapped between the falling slab and the tent floor, which was placed on compacted snow reinforced by skis.
The slope immediately above the tent was steeper than is readily apparent by sight or photograph, and all it takes to crush your chest is half a cubic meter of snow.
Hijinks are still on offer, though, courtesy of a handsome-looking Premium TV Drama treatment of the incident. Alas, it's in Russian and there doesn't seem to be subs yet.
Besides, all the weirdness after the flight from the tent is still up for debate. And if the worst injuries were sustained in the tent, we now have to explain how and why those dying people walked off, half-naked, in appalling weather, only to die in a stream at least a mile away.
Here's footage of a small, intentionally-triggered slab avalanche on a mild gradient perhaps a little steeper than the one camped on at Dyatlov. If it doesn't look like much, remember: 0.125 to 0.5 m3.
UPDATE: Below, a video explaining the new science. They do some experimenting on a hillside at the Dyatlov gradient and it's stark how much steeper it is than the photos from the scene suggest.